Experimental and modeling demonstration of stronger population suppression by gene drive targeting doublesex from dominant female-sterile resistance alleles.

CRISPR homing drives can be used to suppress a population by targeting female fertility genes. They convert wild-type alleles to drive alleles in the germline of drive heterozygotes, but resistance alleles can weaken suppressive power, or even stop suppression if they preserve the function of the target gene. We use multiplexed gRNAs targeting doublesex in Drosophila to avoid functional resistance and create resistance alleles that were dominant female-sterile. This occurs because male doublesex transcripts are generated in females by disruption of the female-specific splicing acceptor. We rescue dominant sterility of the drive by providing an alternate splicing site. It is thus recessive female sterile, and has efficient drive conversion in both sexes. Dominant-sterile resistance alleles enable stronger suppression in computational models, even in the face of modest drive efficiency and fitness costs. However, we find that male drive homozygotes were sterile. Attempts to rescue males with alternate expression are not successful, though some male homozygotes have less severe intersex phenotypes. While this negatively impacts the drive, models show that it still has significantly improved suppressive power compared to standard drives. Therefore, this design may have wide applicability to suppression gene drives in a variety of organisms with intermediate drive performance.